Teaching machine with servo-controlled track selector

ABSTRACT

A teaching machine for selectively reproducing the respective audio tracks on a record drum lengthwise thereof has a servocontrolled track selector wherein a drive motor rotates the drum through a slip-clutch, and a series of ratchet wheels on the shaft of the drum are offset by fractional tooth differences and are engageable by respective pawls to stop the drum at as many different positions as the number of ratchet wheels times the number of teeth on each ratchet wheel. The pawls are actuated by respective solenoids controlled by a commutator operated by the drum shaft. The commutator has radially spaced brushes connected respectively to the solenoids, and has as many segments as the teeth on each ratchet wheel. Further, the portions of each segment engageable by the respective brushes are offset the same as are the teeth of the ratchet wheels. By selecting the circuits of the respective brushes and segments, the solenoids are actuated selectively to cause the drum to be indexed. By also selecting between one or another of two side-by-side heads spaced by an odd multiple of one-half the distance between successive index positions, the number of audio tracks which can be selected is doubled.

51 Aug. 8, 1972 TEACHING MACHINE WITH SERVO- CONTROLLED TRACK SELECTOR Primary ExaminerLeonard Forman Assistant Examiner-Dennis A. Dearing Att0rneyGeorge H. Fritzinger ABSTRACT A teaching machine for selectively reproducing the respective audio tracks on a record drum lengthwise thereof has a servo-controlled track selector wherein a drive motor rotates the drum through a slip-clutch, and a series of ratchet wheels on the shaft of the drum are offset by fractional tooth differences and are engageable by respective pawls to stop the drum at as many different positions as the number of ratchet wheels times the number of teeth on each ratchet wheel. The pawls are actuated by respective solenoids controlled by a commutator operated by the drum shaft. The commutator has radially spaced brushes connected respectively to the solenoids, and has as many segments as the teeth on each ratchet wheel. Further, the portions of each segment engageable by the respective brushes are offset the same as are the teeth of the ratchet wheels. By selecting the circuits of the respective brushes and segments, the solenoids are actuated selectively to cause the drum to be indexed. By also selecting between one or another of two sideby-side heads spaced by an odd multiple of one-half the distance between successive index positions, the number of audio tracks which can be selected is dou- 6 Claims, 6 Drawing Figures [72] Inventor: Bruce N. Whitlock, Morris Plains,

[73] Assignee: McGraw-Edison Company, Elgin,

Ill.

[22] Filed: June 15, 1970 [21] Appl. No.: 46,013

[52] US. Cl. ..274/4 J, 179/1001 PS, 274/9 RA, 274/17, 340/1741 C [51] Int. Cl. ..Gl 1b 21/08, G1 lb 25/02 [58] Field of Search ..274/4 J, 9 RA, 17, 20-22; 179/1002 T; 340/174.1 C; 74/527 [56] References Cited UNITED STATES PATENTS 2,399,906 5/ 1946 Bently ..74/527 2,702,609 2/1955 Frazier ..74/527 2,777,336 1/1957 Schonstedt ..74/527 2,953,383 9/1960 Walters ..274/15 2,953,384 9/1960 Walters ..274/17 3,176,083 3/1965 Hauser 179/1002 T b]ed 3,383,114 5/1968 Ryan ..274/1 A 3,424,872 1/1969 Whitlock ..35/35 C PATENTEDAHB 8 I 72 SHEET 1 OF 4 AGENT PATENTED M19 3 I973 SHEET 2 [IF 4 PATENTED NIB 8 I973 SHEET 3 [IF 4 INVENTOR, BRUCE N. WHITLOCK AGENT PATENTEDAHB 8 i972 sum 9 BF 4 FIG. 6

AUD/O AMP OQOOO 00000 00000 00000 00000 OOOOO OOOOO INVENTOR.

BRUCE N. WHITLOCK AGENT TEACHING MACHINE WITH SERVO- CONTROLLED TRACK SELECTOR It is an object of my invention to provide a servo-controlled track selector which is of a simple and positive construction and which is more economical to produce than those of the prior art.

Another object is to provide such track selector which is operable dependably to select respective tracks responsive to a code machine.

Another object is to provide such track selector wherein a set of tracks on a rotating drum is scanned repeatedly 10 and the drum is stopped instantly when a selected track is reached.

Another object is to drive such drum through a slipclutch and to latch the drum to a quick stop by a pawl and ratchet mechanism the instant a selected track is reached.

Another object is to provide a multiplicity of pawl and ratchet wheels each with relatively coarse teeth and with a durable pawl, and to provide a fine selection by staggering the ratchet wheels so that the teeth are offset by a fractional tooth distance depending on the number of the ratchet wheels.

Another object is to provide an easily mountable and removable drum for such machine wherein each drum is held accurately against eccentricity and is located always in the same angular position about the drum shaft.

These and other objects and features of the invention will be apparent from the following description and the appended claims.

In a description of my invention, reference is had to the accompanying drawings, of which:

FIG. 1 is a top plan view of a teaching machine construction including an audio drive and a servo-controlled track selector according to the invention;

FIG. 2 is a fractional rear view of the teaching machine;

FIG. 3 is a left-hand section on the line 3-3 of FIG.

FIGS. 4 and 5 are right-and left end views of the teaching machine; and

FIG. 6 is a circuit diagram of the servo-controlled system.

The present servo-controlled track selector has a frame including a rectangular base plate 10 provided with a front lateral standard 11 and with four parallel transverse standards of which there is a left standard 12, two intermediate standards 13 and 14 and a right standard 15. A motor 16 of a servo system is mounted on the base plate back of the standard 12 via a bracket 17 and is coupled through a pair of O-ring belts 18 to a lateral shaft 19. This shaft is journaled at its rightend in a bearing 20 mounted in the front portion of the standard 13 and is journaled 20 near its left end in a bearing 21 mounted in the back portion of the standard 12. The shaft 19 has a drive gear 22 meshing with a gear 23 journaled on a lateral shaft 24 positioned ahead of the shaft 19 in parallel relation thereto. The gear 23 is retained frictionally between a disk 25 riveted to the shaft 24 and a second disk 26 splined to this shaft, the disks being under pressure of a spring 27 to provide a slip-clutch for coupling the servo motor 16 to the shaft 24. The shaft 24 is journaled just to the right of the slipclutch 25-27 in a bearing 28 mounted in the standard 12 and is journaled midway its length in a bearing 29 in the standard 14. The shaft 24 extends beyond the standard 14 to the right end of the base plate. A collar 30 on the shaft 24 to the right of the standard 14 serves in connection with the disk 25 at the left of the standard 12 to hold the shaft against end play.

Mounted slidably on the shaft 24 just to the right of a collar 30 is a frusto-conical locator cap 31 for a record cylinder or drum 32. The locator cap is biased rightwardly against a stop ring 33 on the shaft 24 by a coil spring 34 bearing against the collar 30. Secured to the right end of the shaft 24 is a cylindrical cup 35 having an internal bearing 36 secured by a pin 37 to the shaft. The record cylinder 32 is open at its inner end and has an end wall at its other end provided with a center hole 38 to receive the end post of the shaft 24 as the record cylinder is mounted. The periphery of the cylinder is covered with a magnetizable material 39 for receiving recorded signals thereon. Secured to the end wall of the cylinder is a U-shaped handle 40 to enable the cylinder to be pressed onto and removed from the shaft 24 without having to place the hand on the recording surface. The cylinder is mounted by sliding it over the cup 35 until the left end presses against a conical surface of the locator cap 31 and displaces the cap from thestop 33. However, as thecylinder is slid onto the cup 35 it is also oriented about the cup until a spring detent 41 on the cup engages a locator hole in the cylinder to retain the cylinder releasably in a mounted position wherein it is always oriented in the same angular position about the shaft 24. To remove the cylinder the user simply takes hold of the handle 40 and draws the cylinder outwardly to overcome the detent 41.

The record cylinder has a teaching program recorded thereon along parallel tracks lengthwise thereof, which may be made by the present machine. The individual tracks bear respective items of information or instruction and are to be played back selectively. The audio drive for the machine may be in accordance with that described in Whitlock vU.S. Pat. No. 3,354,557, dated Nov. 28, 1976. For example, a drive motor 42 as of the shaded pole type may be coupled through a belt reduction 43 to a flywheel 44. This flywheel has a shaft journaled in a bearing 45 in the standard 14. A pinion 46 on the shaft is in mesh with a larger gear 47 journaled on the left end of a long lead screw 48. This lead screw is journaled in the standard 13 at its left end and in the standard 14 at its right end. A spring clutch 49 couples the gear 47 to the lead screw when a solenoid 50 is actuated. Meshing with the lead screw 48 is a nut 51 of a head carriage assembly 52. The nut is secured to a carriage base structure 53 which has a bearing 54 slidably engaging a cross rod 55 supported at its ends by the standard 14-15. Slidably mounted on the top face of the base structure 53 for movement from front-to-back is a plate 56 carrying a record-reproduce head 57 which is biased by a spring 58 against the record cylinder 39. At the back end of the plate 56 is a screw 59 which depends past the back edge of an upright bail 60. This bail is pivoted at its ends to studs 61 carried by respective brackets 62 secured to the base plate 10. The bail is connected to a solenoid 63 which when energized rocks the bail rearwardly to move the record-reproduce head 57 away from the record drum 39. When the head carriage switches 65 and 66, to perform respective control functions later described.

When the clutch solenoid 50 is energized its armature 50a is drawn with pressure against the outer end of the clutch spring 49 causing the spring instantly to be drawn frictionally about the lead screw 48 to couple the gear 47 to the lead screw. This causes the head carriage assembly 52 to be moved from right to left along the record cylinder to either record on or reproduce from a track on the cylinder depending on whether the machine is in recording or reproducing condition. As the lead screw is turned it winds up a helical spring 67 at its outer end housed in a cylindrical case 68 on the standard 15. When the head carriage reaches its left end of travel it closes the end switch 65 to energize the solenoid 63 and draw the head 57 out of contact with the record cylinder and to deenergize the clutch solenoid 50 whereby to release the clutch spring 49 and allow the return spring 67 to spin the lead screw 48 in a reverse direction to return the head carriage assembly quickly to home position. When the head carriage reaches its home position the end switch 66 allows the solenoid 63 to be deenergized and permit the spring 58 to return the head into engagement with the record cylinder. The drive clutch solenoid 50 is not again actuated until a start control (not shown) is operated. Thus, for any position of the record cylinder the machine can be operated to record on or to reproduce from a respective track on the cylinder.

The servo-controlled track selector with which the present invention is particularly concerned is adapted forindexing the record cylinder to any one of 78 different positions and to select one or another gaps of the head whereby to select the operation along any one of 156 tracks. This servo mechanism comprises three ratchet wheels 69a, 69b and 690 pinned to the portion of the shaft 24 between the standards 12 and 14. The ratchet wheels are engageable by respective pawls 72a, 72b and 72c held normally disengaged .by respective springs 75a, 75b and 75c. (See FIG. 3). The pawls are engaged with the respective ratchet wheels by respective solenoids 78a, 78b and 780 mounted on the front standard 11. Each ratchet wheel 69a, 69b and 69c has for example 26 teeth to enable each ratchet wheel and respective pawl to stop the record cylinder in any one of 26 equally spaced positions. However, the ratchet wheels are offset by one-third tooth distance from each other to render the three ratchet wheels operative to stop the record cylinder in any one of 78 equally spaced positions. In addition, the head 57 is provided with two gaps spaced circumferentially about the drum by one one hundred fifty-six revolution of the-drum (one-half of the distance between the successive 78 indexing positions) to enable the machine by selection of one or the other of the two head gaps and by a selective time operation of the ratchet pawls to bring the 156 different tracks into selective engagement with the heads.

A selective activation of the solenoids 78a, 78b and 78c as well as a timing of the actuation of these solenoids comprises a circuit as shown in FIG. 5. This circuit includes a commutator 81 (FIGS. 1, 5 and 6) mounted on a bracket 82secured to the base 10. The

commutator includes a brush arm 83 mounted on the left end portion of the shaft 24. This brush arm carries three individual brushes 84a, 84b and 840 equally radially spaced therealong. The brushes are connected respectively to individual stationary slip-rings 87a, 87b and 870 through individual brushes 88a, 88b and 88c. The slip-rings are connected respectively to the solenoids 78a, 78b and 780. Further, the commutator includes 26 equally spaced segments 93 wherein each segment has three portions 93a, 93b and 93c, corresponding to the respective brushes 84a, 84b and 840, which are stepped from each other by one-third the angular distance between the successive segments. With reference to FIG. 6, a d. c. power source, say a battery 94, is connected selectively by a switch 95 to the commutator segments 93. The return circuit to the battery is completed via the brushes 84 and respective sliprings through one or another of the solenoids 78a, 78b and 780 determined by a switch 96. Another switch 97 connects one or the other of the gap coils of the head 57 to an audio amplifier. These switches 95, 96 and 97 are connected by respective lines 98, 99 and 100 as to a keyboard 101 (diagrammatically shown) having individual keys which may be operated to select the different combinations of the switches 95, 96 and 97 which will index the record cylinder 39 and select one or the other of the gaps of the head 57 to record on or play back from any selected one of the 156 individual tracks on the record cylinder. At the end of playing or recording a track a common knock-out bail 102 for the pawls 72a, 72b and 72c is turned by a solenoid 103 to disengage whichever of the pawls was last actuated. This causes the motor 16 to start turning the record drum.'In a subsequent indexing operation a selected segment and selected brush slip-ring are made active on the commutator so that when the selected brush reaches the selected segment current will flow through the respective pawl solenoid to engage its pawl with the selected tooth and bring the record'drum to'a sudden stop. At the end of the indexing operation the audio drive system is started by the solenoid 63 operating the bail 60 to engage the head 57 with the record drum and by the clutch solenoid 50 engaging the drive clutch 49 to start a progressive movement of the head 57 along the drum.

The embodiment of my invention herein particularly shown and described is intended to be illustrative and not necessarily lirnitative of my invention since the same is subject to changes and modifications without departure from the scope of my invention which I endeavor to express according to the following claims.

Iclaim:

1. A servo system comprising a record drum having individual tracks thereon parallel to the axis thereof,

drive means including a slip clutch for rotating said drrun, a plurality of ratchet wheels on said shaft and of corresponding pawls and solenoids, each of said ratchet wheels having a plurality of equally spaced teeth wherein the teeth of said respective ratchet wheels are shifted circumferentially'from each other by a fractional tooth separation in inverse proportion to the number of said ratchet wheels, circuit means including a commutator on the shaft of said drum and switch means for selectively connecting to the segments of said commutator and to said solenoids for selectively activating said solenoids to stop said drum with slippage of said clutch at preselected index positions, wherein said commutator includes a plurality of radially spaced brushes connected respectively to said solenoids, and wherein the portion of said segments engageable by said respective brushes are offset circumferentially by a fractional distance between successive segments in inverse proportion to the number of said ratchet wheels.

2. The servo system set forth in claim 1 including an audio system having a multiple track magnetic head engageable with said record drum along two side-by-side tracks spaced by an odd multiple of one-half the distance between successive index positions on said drum, and wherein said circuit means includes switch means for selectively connecting said dual head to said audio circuit upon each operation of said servo system.

3. In a servo system for selectively engaging parallel tracks of a record drum with a translating head: the

combination of a rotatably mounted record drum bearing a plurality of said tracks equally spaced thereabout, a drive motor, a coupling including a slip-clutch between said motor and said drum, a plurality of ratchet wheels secured to said drum and of corresponding pawls, the number of tracks on said drum being an integral multiple of the number of teeth on each of said ratchet wheels, and said ratchet wheels being circumferentially displaced from each other by a fraction of a tooth distance in inverse proportion to the number of said ratchet wheels, said pawls being engageable with said ratchet wheels to stop said drum against the driving force of said motor transmitted via said slip-clutch, a commutator coupled to said drum having a brush and V corresponding slip ring for each of said ratchet wheels and as many segments as the number of teeth on each of said ratchet wheels, each of said segments of said commutator having respective portions engageable by said brushes which are stepped circumferentially from each other by a fraction of the distance between successive segments in inverse proportion to the number of said ratchet wheels, respective solenoids for controlling said pawls, and circuit means for controlling said solenoids including a servomechanism for selecting one of said segments and concurrently one of said brushes whereby the selected solenoid is operated when a selected brush engages the respective portion of a selected segment.

4. The servo system set forth in claim 3 including an audio drive system for moving a magnetic head along a selected track, and means for activating said drive system upon selection of a given commutator segment and brush by said servo system.

5. The servo system set forth in claim 4 including a means for engaging the record-reproduce head with a selected track and for starting said drive system to advance the head along said track, and a bail and activating solenoid for disengaging whichever of said pawls is engaged with the respective ratchet wheel when the head reaches the end of said track.

6. The servo system set forth in claim 5 including two tracks on said drum for each index position thereof, a dual record-reproduce head for engaging both of said tracks in each of said index positions, and means controlled by said servo system during each operation thereof for selectively connecting one of said recordreproduce heads to s aid audio c ircgit. 

1. A servo system comprising a record drum having individual tracks thereon parallel to the axis thereof, drive means including a slip clutch for rotating said drum, a plurality of ratchet wheels on said shaft and of corresponding pawls and solenoids, each of said ratchet wheels having a plurality of equally spaced teeth wherein the teeth of said respective ratchet wheels are shifted circumferentially from each other by a fractional tooth separation in inverse proportion to the number of said ratchet wheels, circuit means including a commutator on the shaft of said drum and switch means for selectively connecting to the segments of said commutator and to said solenoids for selectively activating said solenoids to stop said drum with slippage of said clutch at preselected index positions, wherein said commutator includes a plurality of radially spaced brushes connected respectively to said solenoids, and wherein the portion of said segments engageable by said respective brushes are offset circumferEntially by a fractional distance between successive segments in inverse proportion to the number of said ratchet wheels.
 2. The servo system set forth in claim 1 including an audio system having a multiple track magnetic head engageable with said record drum along two side-by-side tracks spaced by an odd multiple of one-half the distance between successive index positions on said drum, and wherein said circuit means includes switch means for selectively connecting said dual head to said audio circuit upon each operation of said servo system.
 3. In a servo system for selectively engaging parallel tracks of a record drum with a translating head: the combination of a rotatably mounted record drum bearing a plurality of said tracks equally spaced thereabout, a drive motor, a coupling including a slip-clutch between said motor and said drum, a plurality of ratchet wheels secured to said drum and of corresponding pawls, the number of tracks on said drum being an integral multiple of the number of teeth on each of said ratchet wheels, and said ratchet wheels being circumferentially displaced from each other by a fraction of a tooth distance in inverse proportion to the number of said ratchet wheels, said pawls being engageable with said ratchet wheels to stop said drum against the driving force of said motor transmitted via said slip-clutch, a commutator coupled to said drum having a brush and corresponding slip ring for each of said ratchet wheels and as many segments as the number of teeth on each of said ratchet wheels, each of said segments of said commutator having respective portions engageable by said brushes which are stepped circumferentially from each other by a fraction of the distance between successive segments in inverse proportion to the number of said ratchet wheels, respective solenoids for controlling said pawls, and circuit means for controlling said solenoids including a servomechanism for selecting one of said segments and concurrently one of said brushes whereby the selected solenoid is operated when a selected brush engages the respective portion of a selected segment.
 4. The servo system set forth in claim 3 including an audio drive system for moving a magnetic head along a selected track, and means for activating said drive system upon selection of a given commutator segment and brush by said servo system.
 5. The servo system set forth in claim 4 including a means for engaging the record-reproduce head with a selected track and for starting said drive system to advance the head along said track, and a bail and activating solenoid for disengaging whichever of said pawls is engaged with the respective ratchet wheel when the head reaches the end of said track.
 6. The servo system set forth in claim 5 including two tracks on said drum for each index position thereof, a dual record-reproduce head for engaging both of said tracks in each of said index positions, and means controlled by said servo system during each operation thereof for selectively connecting one of said record-reproduce heads to said audio circuit. 